Glass-treating furnaces, such as used in tempering systems, employ rollers driven by belts, or chains and sprockets, to form a conveyor for carrying glass through the heating and quenching sections. The rollers are formed of a ceramic material so as to withstand the heat in the furnace. They are usually directly engaged by the belt or chains which are used to effect the rotation of the rollers. Further, the rollers usually have pins or other projecting elements which are received in slots or openings whereby the rollers are fixed vertically and horizontally. The glass rests directly on the rollers and is moved along by rotation of the rollers. It is known that the glass must be oscillated when it is in the furnace section in order to ensure uniform heating and to prevent breakage, crazing or other undesirable results. The glass cannot be simply heated or quenched while it is motionless. It must be rotated back and forth so that the temperature does not vary along the sheet of glass.
Direct drive of the rollers by a chain involves direct contact between the chain and the rollers or the chain sprockets and the rollers. When connecting a metal or other composition type sprocket, to a ceramic or similar type roller, no matter what the mode of connection involves, one will always be faced with the matter of unlike substances expanding and/or contracting (due to the heat cycling involved in normal operation), thus causing seperation, cracking and even complete fracture, at the point of connection. Direct drive by a belt can result in damage to the belt, and/or the roller. Damage to the roller occurs due to the abrasion between the roller and the steel type flat belt. This can be substantially lessened through the use of a cloth or composition drive belt. However, to date the cloth and/or composition belt, has been limited in its usefullness. It has been observed, that while the cloth type belts do work rather well in the shorter length equipment, (approximately fifty feet and under), the longer equipment tends to encounter far greater stresses than can be tolerated by the cloth type materials now available.
Being forced, thus far, to use the steel type belts on the longer equipment, one has had to accept the roller wear, along with frequent belt damage. This belt damage, is generally due to particles of foreign material, (namely pieces of glass), becoming lodged between said belt and the flat surfaced drive wheels. The pressure normally present between these two surfaces being very great, causes an indentation upon said flat belt. These dents are very undesirable, as they create a lifting effect upon the rollers as the dents pass under.
Further, the use of pins or shafts received within the rollers, as a means for guiding the rollers, creates move problems. Very often the rollers will fail at the point of connection between the pins and the rollers. One common method is to wedge a pin into the roller itself. This is a source of stress, particularly under the high temperatures encountered. On occasions pins will fail and they must be replaced. There is further danger of damaging the rollers when this is done.
McMaster U.S. Pat. No. 3,994,711 shows the use of pin-like extensions on the rollers coupled with slots, and/or positioning members which cooperate with reduced extensions of the rollers, as a means for maintaining positions of the rollers. The McMaster patent also shows directly driving the rollers by the chain.
The present invention provides a guiding and supporting arrangement for the rollers which does not require pins or other projections from the roller, and a drive in which the roller is not directly engaged with a chain or belt. The invention provides a self-centering conveyor roller system, and a system in which the rollers are of uniform size and shape throughout their length. They do not require any inserted pins, nor do they have any reduced sections or the like at their ends. Nonetheless, they will remain in proper position. They also will be driven without the need for direct contact with the belt or chain. The invention further provides a system in which the rollers can be easily removed and replaced. They simply rest upon driving means from which they can be lifted off without any concern for their relationship within pin receiving openings or guides.